"We currently know that there were three dead and seven injured," police spokesman Kurt Graf told the dpa news agency, adding that the shooter was among those killed, without saying whether he had committed suicide or been shot by police.

Some Swiss media were quick to claim that the gunman was a disgruntled employee, the local paper Willisauerer Bote reported that the company had just announced it was cutting production after a poor logging season.

Police said that rescue services had been deployed immediately and the area had been sealed off.

A hotline was set up for families and workers of the Kronospan factory, which according to the local town council, has some 450 employees.

The mayor of Menzau, Adrian Duss, described the incident as a tragedy.

Switzerland has a tradition on gun ownership, as most of its military are reservists who keep their weapons stored in their homes under strict regulations.

The country ranks third in figures for gun ownership after the United States and Yemen.

The previous shooting rampage incident in Switzerland happened in January 2013 when a man killed three people and wounded two more in the village or Daillon in the South of the country.